Combination of Digital Self-Interference Cancellation and AARFSIC for Full-Duplex OFDM Wireless

International audienceFull-Duplex radio provides many benefits beyond improving spectral efficiency. However, canceling the self-interference completely is a big challenge behind Full-Duplex wireless. Although many intelligent efforts devote to active analog radio frequency self-interference cancellation (AARFSIC), the power of the residual self-interference (SI) after the AARFSIC is still much stronger than that of the receiver thermal noise. In this paper, we first study deeply the AARFSIC and "dig" the core problem that causing the residual SI, and then propose a digital self-interference cancellation in time domain (DSICT) to complement AARFSIC for the Full-Duplex OFDM wireless. The ADS-Matlab co-simulation results demonstrate the actual performance and show that the residual SI after the AARFSIC can be canceled completely by employing the proposed DSICT

Digital I/Q Imbalance Correction for Full-Duplex Dual-Band OFDM Radio Transceivers I Introduction

International audienceThis paper presents a Full-Duplex Dual-Band (FDDB) OFDM radio architecture that enables the radio transceiver to be more flexible and provides a viable radio link capacity gain. A simple but practical I/Q imbalance estimation and compensation method, based on the frequency-flat-fading behavior of the self-interference channel, is proposed. The performance of the proposed I/Q imbalance compensation method is evaluated by system level simulations conducted with ADS and Matlab. The co-simulation results show that the proposed radio transceiver could potentially increase the physical layer transmission rate by four times compared to the conventional radio link at the cost of tolerable loss of BER performance. The I/Q imbalance compensation method can effectively compensate both high and low I/Q imbalance without the problem of algorithm convergence

ULTRA-WIDEBAND NONLINEAR ECHO-CANCELLATION

Hybrid fiber coaxial (HFC) networks are used around the world to distribute cable television and broadband internet services to customers. These networks are governed by the Data-Over-Cable Service Interface Specification (DOCSIS) family of standards, with the most recent version at the time of this writing being DOCSIS 3.1. A frequency division duplex (FDD) spectrum is used in DOCSIS 3.1, where the upstream and downstream signals are separated in frequency to eliminate interference. A possible method to increase signal bandwidths is to use a full-duplex (FDX) spectrum, in which the US and DS signals use the same frequencies at the same time. A main challenge faced when implementing FDX in a DOCSIS node is eliminating the interference in the received US signal caused by the transmitted DS signal. One possible method for eliminating the interference is utilizing an echo-canceling algorithm, which predicts the self-interference (SI) based on the known DS signal and cancels it from the received US signal. Although echo-cancellation algorithms exist for fundamentally similar applications, the DOCSIS FDX case is more complicated for two main reasons. First, the DOCSIS node uses a nonlinear power amplifier to amplify the DS signal. Second, the DS signal is an ultra-wideband signal spanning a frequency range of up to 1.2 GHz. Most of the amplifier modeling techniques discussed in the literature were designed for narrowband wireless signals and will have limited performance when used with ultra-wideband signals. This thesis develops an algorithm to characterize the power amplifier and to predict the harmonics it generates for a given DS signal. These predicted harmonics can be used to cancel the SI signal in a full duplex DOCSIS system. The algorithm, which is referred to as the ultra-wideband memory polynomial (UWB-MP) model, is based on the well-known memory polynomial model with adaptations which allow the model to predict harmonics for ultra-wideband signals. Since a direct implementation of the UWB-MP model in an FPGA would result in very high resource usage, system architecture recommendations are provided. Our proposed implementation of the model compensates for harmonics up to and including the 3rd order, which has a power spectrum extending above 3600 MHz. Using the techniques discussed in this thesis, it is shown that a sampling rate of 4 GHz allows for cancellation of the SI signal while providing a reasonable balance between performance and resource usage. Matlab simulations of a DOCSIS node with various parameters and PA simulation models were conducted. The simulations showed that over 75 dB of cancellation of the SI signal is possible in an idealized hardware setup. It is also demonstrated that AWGN injected into the received signal does not reduce the ability of the model to estimate the PA harmonics, although the noise itself cannot be canceled. Further simulations showed that the UWB-MP model could cancel harmonics whose power is much higher than that specified in DOCSIS. Although the UWB-MP model was designed with memory polynomial type PAs in mind, simulation results show that significant cancellation is possible with PAs that are represented by Wiener models as well. Based on the simulation results, we recommend using a filter of length 20 coefficients for each harmonic in the UWB-MP model, and 60 iterations with 500 samples for estimating the coefficients with the least squares method

Conception d’une architecture pour Full-Duplex basée sur les émetteurs-récepteurs radio

The wireless medium is a shared and limited resource. Current wireless standards always share the medium with Half-Duplex principle: the transmission and reception of signals are done in two separate time slots or two different frequency bands. Besides, the transceiver can only transmit and receive one signal at a time. This dissertation takes an alternate approach: Instead of sharing the medium with Half-Duplex principle, the entire licensed frequency band is shared for simultaneous transmission and reception, which we call Full-Duplex. Besides, the design concept for a wideband flexible radio transceiver can process two different types of signals at a time. To approach this goal, we use an active analog radio frequency self-interference cancellation (AARFSIC) method or a combination scheme of the AARFSIC and active digital self interference cancellation in time domain (ADSICT) to cancel the strong self-interference (SI) induced by the Full-Duplex principle. Based on the Full-Duplex radio, we propose a flexible Full-Duplex Dual-Band (FDDB) OFDM radio transceiver by combining it with a Dual-Band RF front-end. Building on these, we make three main contributions: We present an active self-interference cancellation (ASIC) scheme, which can cancel both the strong one-path and multi-path SI completely, based on the combination of the AARFSIC and DSICT. Next, we introduce the design and evaluation of a Full-Duplex OFDM radio, including the analysis and qualification of the impact of the thermal noise and phase noise on the system performance. Finally, we develop a FDDB OFDM radio that can work on two separate spectrum fragments. In order to eliminate the impact of the I/Q imbalance on the FDDB radio, a simple but practical digital I/Q imbalance estimation and compensation method is presented. The system level simulation conducted with ADS and Matlab software shows that this method can effectively compensate both high and low I/Q imbalance.Le medium sans fil est une ressource partagée et limitée. Les normes sans fil actuelles partagent toujours le principe de partage du medium Half-Duplex: la transmission et la réception de signaux sont effectuées dans deux intervalles de temps distincts ou deux bandes de fréquences différentes. En outre, l'émetteur-récepteur ne peut émettre et recevoir qu’un signal à la fois. Cette thèse suit une autre approche: au lieu de partager le support avec le principe de Half-Duplex, toute la bande de fréquence autorisée est partagé pour la transmission et la réception simultanée, approche qui est appelée Full-Duplex. Dès lors, on peut concevoir une architecture d'un émetteur-récepteur radio flexible à large bande pour traiter deux types de signaux différents à la fois. Pour approcher cet objectif, nous utilisons une méthode de suppression active analogique de l’auto-interférence (AARFSIC) et l'annulation active numérique d'auto interférence dans le domaine temporel (ADSICT) pour annuler la forte auto-interférence (SI) induite par le principe Full-Duplex. Basé sur la radio Full-Duplex, nous proposons un système flexible Dual-Band (FDDB) émetteur-récepteur radio OFDM-Full Duplex en la combinant avec un front-end RF double bande. S'appuyant sur ces principes, nous exposons trois contributions principales: Nous présentons une technique d’annulation analogique de l’auto-interférence (ASIC), qui peut annuler complètement l’auto-interférence à trajet direct ou multi-trajets, basée sur la combinaison des méthodes AARFSIC et DSICT. Ensuite, nous présentons la conception et l'évaluation d'une radio OFDM Full-Duplex, y compris l'analyse et la qualification de l'impact du bruit thermique et du bruit de phase sur les performances du système. Enfin, nous développons une radio dual-bande FDDB OFDM qui peut fonctionner sur deux fragments de spectre séparés. Afin d'éliminer l'impact du déséquilibre I/Q sur la radio FDDB, une méthode d’estimation des déséquilibres I/Q et de compensation, simple mais efficace, est présentée. La simulation au niveau système menée avec ADS et Matlab montre que cette méthode peut effectivement compenser des déséquilibres I/Q aussi bien élevés que faibles

Concept de design d'émetteurs-récepteurs radio flexibles basés sur la technologie Full-Duplex

The wireless medium is a shared and limited resource. Current wireless standardsalways share the medium with Half-Duplex principle: the transmission and receptionof signals are done in two separate time slots or two different frequency bands.Besides, the transceiver can only transmit and receive one signal at a time.This dissertation takes an alternate approach: Instead of sharing the medium withHalf-Duplex principle, the entire licensed frequency band is shared for simultaneoustransmission and reception, which we call Full-Duplex. Besides, the design conceptfor a wideband flexible radio transceiver can process two different types of signals ata time.To reach this goal, we propose to use an active analog radio frequency (RF) selfinterferencecancellation (AARFSIC) method or a combination scheme of the AARFSICand active digital self-interference cancellation in time domain (ADSICT) to cancelthe strong self-interference (SI) induced by the Full-Duplex principle. Based on theFull-Duplex radio, we propose a flexible Full-Duplex Dual-Band (FDDB) OFDM radiotransceiver by combining the Dual-Band RF front-end.Building on these, we make three main contributions: We present an active selfinterferencecancellation (ASIC) scheme, which can cancel both the strong one-pathand multi-path SI completely, based on the combination of the AARFSIC and DSICT.Next, we introduce the design and evaluation of a Full-Duplex OFDM radio, includinganalysis and qualification of the impact of the thermal noise and phase noise onthe system performance. Finally, we develop an FDDB OFDM radio that can work ontwo separate spectrum fragments. In order to eliminate the impact of the I/Q imbalanceon the FDDB radio, a simple but practical digital I/Q imbalance estimation andcompensation method is presented. The system level simulation conducted with ADSand Matlab software shows that this method can efficiently compensate both high andlow I/Q imbalance.Le medium sans fil est une ressource partagée et limitée. Les normes sans filactuelles partagent toujours le principe de partage du medium Half-Duplex: la transmissionet la réception de signaux sont effectuées dans deux intervalles de temps distinctsou deux bandes de fréquences différentes. En outre, l’émetteur-récepteur nepeut émettre et recevoir qu’un signal à la fois.Cette thèse suit une autre approche: au lieu de partager le support avec le principede Half-Duplex, toute la bande de fréquence autorisée est partagé pour la transmissionet la réception simultanée, approche qui est appelée Full-Duplex. Dès lors, on peutconcevoir une architecture d’un émetteur-récepteur radio flexible à large bande pourtraiter deux types de signaux différents à la fois.Pour approcher cet objectif, nous utilisons une méthode de suppression activeanalogique de l’auto-interférence (AARFSIC) et l’annulation active numérique d’autointerférencedans le domaine temporel (ADSICT) pour annuler la forte auto-interférence(SI) induite par le principe Full-Duplex. Basé sur la radio Full-Duplex, nous proposonsun système flexible Dual-Band (FDDB) émetteur-récepteur radio OFDM Full-Duplexen la combinant avec un front-end RF double bande.S’appuyant sur ces principes, nous exposons trois contributions principales: Nousprésentons une technique d’annulation analogique de l’auto-interférence (ASIC), quipeut annuler complètement l’auto-interférence à trajet direct ou multi-trajets, baséesur la combinaison des méthodes AARFSIC et DSICT. Ensuite, nous présentons la conceptionet l’évaluation d’une radio OFDM Full-Duplex, y compris l’analyse et la qualificationde l’impact du bruit thermique et du bruit de phase sur les performances dusystème. Enfin, nous développons une radio dual-bande FDDB OFDM qui peut fonctionnersur deux fragments de spectre séparés. Afin d’éliminer l’impact du déséquilibreI/Q sur la radio FDDB, une méthode d’estimation des déséquilibres I/Q et decompensation, simple mais efficace, est présentée. La simulation au niveau systèmemenée avec ADS et Matlab montre que cette méthode peut effectivement compenserdes déséquilibres I/Q aussi bien élevés que faibles